Comparisons of murine micron chains obtained from cell surface or secreted IgM will be made to understand the mechanism of attachment of IgM to the cell surface. A photoactivatable cross-linking agent will be used to determine whether IgD or IgM bind to other cell surface molecules after interaction with specific ligands. The function of different B cell subsets isolated by virtue of their cell surface markers on the fluorescent activated cell sorter will be investigated. Transformation of B cells by Abelson virus will be studied in order to determine susceptible subsets, alteration in surface markers in transformed cells, to build a library of cell lines representing different stages of differentiation, and to study differentiation in neoplastic B cells. The interaction of antigen-pulsed macrophages and selected specific T cells will be studied in order to determine the molecular and cellular events underlying binding, activation, and dissociation of the two cell types with particular emphasis on the level of expression of Ir genes and the biochemical nature of the T cell receptor. Functional correlates of this type of cell interaction will also be pursued as well as an attempt to produce antigen reactive T cell hybrids and those that secrete biologically active factors. T cell recognition of virus infected cells will be analyzed in an attempt to determine if virion polypeptides and products of the MHC have become attached using immunofluorescent assays as well as crosslinking reagents, and to determine if virus infection can alter products of the MHC through metabolic processes e.g., alteration of the carbohydrate moiety of H-2 antigen. The structure of cell surface gene products of chromosome 17 will be investigated with particular emphasis on the use of single dimension peptide mapping and the use of two differential labels to compare gene products. This will permit isolation of common peptides among such gene products for amino acid sequencing in order to determine structural homology.